1. The Field of the Invention
The present invention relates generally to optical transceiver modules. More specifically, the present invention relates to lead frame connectors used to connect an optical subassembly to a printed circuit board in an optical transceiver module.
2. Background and Relevant Art
Optical transceivers are used to transmit and receive optical signals from an optical network and to enable electrical network components to interface with and communicate over optical networks. Many optical transceivers are modular and are designed in accordance with electrical requirements, and other characteristics and requirements of the transceivers. For example the Small Form-Factor Module Multi-Source Agreement (SFF MSA), the Small Form-Factor Pluggable Module Multi-Source Agreement (SFP MSA) and the 10 Gigabit Small Form Factor Pluggable Module Multi-Source Agreement (XFP MSA) Revision 3.1 define such standards and are incorporated herein by reference.
The basic optical components of conventional transceivers include a transmitter optical subassembly (TOSA) and a receiver optical subassembly (ROSA). The TOSA receives electrical signals from a host device via circuitry of the transceiver module and generates a corresponding optical signal that is then transmitted to a remote node in an optical network. Conversely, the ROSA receives an incoming optical signal and outputs a corresponding electrical signal that can then be used or processed by the host device.
The electrical connections between the optical subassemblies and a printed circuit board (PCB) in the transceiver module have various electrical and mechanical requirements. One of the most common electrical connection components used in conventional optical transceiver modules is a flexible printed circuit board, or “flex circuit,” that connects the rigid printed circuit board of the module to leads associated with the TOSA or ROSA. Flex circuits have several advantages, including good electrical performance and radio frequency response and the ability to take up tolerances in the modules and to withstand stresses that arise during manufacture and operation of the modules. Examples of flex circuits used in optical transceiver modules are described in U.S. patent application Ser. No. 10/409,837, filed Apr. 9, 2003, which is incorporated herein by reference. The foregoing patent application also illustrates other components of optical transceiver modules, such as TOSAs and ROSAs, and includes other general information regarding optical transceiver modules that is useful as background material for the invention described herein.
While flex circuits have been widely used in recent years in optical transceiver modules, flex circuits represent a significant portion of the costs and labor required to manufacture transceiver modules. As the price of transceiver modules drops, the costs associated with flex circuits continue to represent an increasing proportion of the overall costs of transceiver modules.
Other approaches to connecting optical subassemblies to printed circuit boards have been introduced in recent years. For example, the leads protruding from TOSAs and ROSAs can be bent into a configuration that enables the leads to be directly soldered or otherwise connected to the printed circuit board. This technique is often less expensive than the use of flex circuits, but can lead to unfavorable RF response due to the inability to carefully control impedances. In addition, bending leads of TOSAs and ROSAs introduces reliability risks due to the likelihood of damaging glass or other fragile portions of header assemblies in TOSAs and ROSAs that enclose the lasers and photodetectors, respectively.
Because of the possibility of damaging the TOSAs and ROSAs and poor electrical performance, bending leads to enable the optical subassemblies to be directly connected to the printed circuit board is not suitable for many transceiver modules. This approach is particularly unsuitable for relatively high-speed transceiver modules, in which the RF response of the conductors is more important.
Furthermore, there exists in the industry an ever-present goal to reduce the overall size of components included in an optical transceiver module. Concurrent with this goal is the need to configure optical transceiver modules that are capable of operating in accordance with recent optical transmission standards and their corresponding optical transmission rates. For instance, transceiver standards are now being developed and utilized to enable optical transceiver modules to transmit and receive optical data at rates of 4, 8, and 10 GBits/second. Any proposed solutions for connecting optical subassemblies in an optical transceiver module or other optical device should satisfy requirements in these areas.